In many industrial plants, particularly chemical plants, the process equipment includes pumps, mixers, or other rotary motion devices that are connected into a large vessel, such as a reactor, or an evaporator. Power for driving the pump, or other rotary motion device, is usually provided by a hydraulic or electric motor. The motor is usually fastened to a solid base, so that the motor housing won't rotate in response to the rotary motion of the pump. It is also common practice to bring the motor shaft and pump shaft into proper alignment at ambient temperatures.
During a process run, however, the large vessel may be subject to much higher or lower temperatures, so that it expands or contracts. When the vessel expands, which is sometimes referred to as "thermal growth", it will move in all three directions, that is, in both horizontal directions, and in a vertical direction. In the case of a vessel having its major dimension along one axis, e.g., the vertical axis, the movement will be mostly in a lengthwise direction, and to a lesser extent, in proportion, in both horizontal directions. Since it is conventional to fasten the motor to a base, or some other support, it can't move along with the vessel and pump as they expand. This places a considerable amount of shear stress and bending stress on the motor and pump shafts and on their bearings.
The present invention overcomes the problems described above. In one embodiment of the invention a lever arm is fastened at its center to the motor housing, instead of being secured to a solid base mounting. Hydraulic oylinders are pivotally connected to each end of the lever arm and to a support member. The piston and rod in each cylinder divide it into two chambers, front and rear. Hydraulic lines connect the chambers of one cylinder to the appropriate chambers of the other cylinder. When the pump, or other rotary motion device, tends to cause rotational movement of the motor housing and lever arm, both cylinders try to move in opposite directions. But, this movement is prevented because the piping that links the cylinders makes the fluid pressure resistance the same for each cylinder. Although the cylinders can't move in opposing directions, they can move in the same direction, at the same time. This capability allows linear displacement of the lever arm, but prevents rotational motion of the arm. The restraining action, therefore, allows the motor to "follow" movement of the vessel with a minimum amount of stress on the shafts and bearings.